The end winding conductors of large turbine generators are conventionally braced or secured by the use of conformable pads or blocks located between the conductors and various support rings that surround the conductors. These pads are usually in the form of a resin-impregnated, resilient material in the form of felt pads or hose-like members.
As discussed in U.S. Pat. No. 3,949,257, which is assigned to the assignee of the present invention, and incorporated by reference herein, the use of pads requires that a supply of different sized pads be provided so as to provide the specific thickness needed. The pads must be tightly fitted so as to keep the conductors tight over the long periods of normal operation. In the improvement described in U.S. Pat. No. 3,949,257, support rings are provided at the inside and outside surfaces of the end winding conductors, with additional support rings disposed between the conductors. Reinforced hoses are disposed between the rings and conductors and extend around the circumference of the rings, which hoses are pressure filled with an epoxy resin that hardens to maintain pressure between the conductors and support rings and provide tight radial support for the end winding conductors.
Such stator coil end blocking is required to prevent excess vibration of the end winding conductors and any cracking or abrasion of components. To do this over the lifetime of the generator with minimum maintenance, the blocking system design should take into account thermal expansion and creep of materials. Many designs incorporate some means of tightening coils in the radial direction using bolts, bands or spring loaded wedges. In designs where a large support ring is used as the backbone to which coils are tied, coils must move very slightly outwardly against the support ring and radial tightness is assured. There still remains, however, a tendency for the end winding conductors to loosen in the circumferential direction about the support ring.
It has previously been proposed to incorporate wedges between all coil ends without any biasing means provided with the wedging. Also, another design uses belleville loaded wedges oriented in a fashion to apply load radially inwardly on the outer diameter of the "basket" formed by the end winding conductors. This method, while serving to provide both a radial load and circumferential load by compressing the end winding conductors from the outside diameter and "arch binding" the winding, precludes the effective use of the simple and more rugged single large support ring.
It is an object of the present invention to provide a securement system for end winding conductors that uses a large support ring around the periphery of the windings and which provides compression of the end winding conductors in both a radial and a circumferential direction.